Eccentric gravel-packed well liner

ABSTRACT

A liner of increased cross-sectional area inside a casing gravel pack is produced by placing the inside pipe eccentrically in the casing. The casing and liner are each prefabricated with an unperforated side and the unperforated side of the liner is placed adjacent to that of the casing. The perforated sides or areas have an annulus space which is gravel packed. The increased cross section area made thus available is used for gas and oil production and/or separation, accommodation of a pump or other well equipment and thus permits increased production.

7 United States Patent Primary Examiner-Marvin A. Champion Assistant Examiner-Ian A. Calvert Attorney-Young and Quigg ABSTRACT: A liner of increased cross-sectional area inside a casing gravel pack is produced by placing the inside pipe eccentrically in the casing. The casing and liner are each prefabricated with an unperforated side and the unperforated side of the liner is placed adjacent to that of the casing. The perforated sides or areas have an annulus space which is gravel packed. The increased cross section area made thus available is used for gas and oil production and/or separation, accommodation of a pump or other well equipment and thus permits increased production.

-[72] Inventor Robert F.Meldau 482,436 Bartlesville, 0151a. 1,918,756 21 AppLNo. 760,583 2,167,190 [22} Filed Sept. 18,1968 2,176,540 [45] Patented Jan. 19, 1971 2,665,644 [73] Assignee Phillips Petroleum Company 2 743 719 a corporation of Delaware 3,039,5 35

[54] ECCENTRIC GRAVEL-PACKED WELL LINER 7Clalms,5l)rawingFigs.

[52] U.S.Cl 166/278, 166/228 [51] Int.Cl. ..E21b43/04 [50] FieldofSearch 166/278, 51,56, 157, 158, 227,228, 236; 103/220; 210/459, 460

[56} References Cited UNITED STATES PATENTS 285,909 10/1883 Matsden 166/227 405,199 6/1889 Chapman 1 66/227X F 'T l q l 1 2 {uni-.1 I t----- l l- ,l7 {3 2 1 +21 l l I l/ l9 \1 1' l l l l 1 l l l l l l l a o o o (b o 0 l I ll 1 1111111: 1 j

INVENTOR. R. F. MELDAU ,1. I l/ I A! A 7' TORNEVS ECCENTRIC GRAVEL-PACKED WELL LINER This invention relates to the production of oil or other fluid from the ground. In one of its aspects it relates to an apparatus comprising a gravel packed liner. In another of its aspects it relates to a method for producing a fluid, such as oil, from the ground employing such a gravel-packed liner.

According to one of its concepts the invention provides an eccentrically disposed, perforate liner within a casing which contains a gravel pack between said liner andthe inner wall of said casing. In another of its concepts the invention provides a combination of a casing, an eccentrically disposed perforate or slotted liner therein and a tailpipe disposed in the space between the liner on the one hand and the casing on the other. In a further concept the invention provides such a combination as here disclosed wherein the space remaining between the casing on the one hand and the liner and the tailpipe on the other is gravel packed. Still further, according to a concept of the invention there is provided a combination or unitary structure of a perforate or slotted liner and a tailpipe, the liner and tailpipe having a nonperforate common wall and being structured by welding or otherwise affixing to the liner wall of an arcuate portion of pipe as more fully described herein.

In some wells poor bottom hole separation of gas and liquid significantly reduces production of such liquid, for example, oil, as in fire flood operation. The use of gravel packs to avoid flow of sand into a well is known. It is also known that in some high-permeability sand, such as Morichal in Venezuela, gas flows from the top of the sand while oil flows substantially from the bottom thereof due to gravity segregation. Until now the oil and gas have become commingled within the liner, following which separation has been attempted up the hole so as to facilitate pumping the oil up through the tubing while allowing the gas to flow up the tubing-casing annulus.

It has now occurred to me that a better approach is to pump the oil from below the sand. In this manner the gas and oil flow separately in the sand and are not mixed in the well. Further, in those cases there fire flood is being effected, it is also necessary to use the tailpipe to permit adding cooling water to the casing annulus without passing the cooling water through the liner.

It has now occurred to me to dispose a perforate or slotted liner eccentrically within the casing to obtain a greater area for gas and oil separation within the well bore or casing which,

of course, is a fixed original size. This permits me to use a larger diameter liner. Thus, in a 7 -inch casing with equal tailpipe flow area, a liner area can be 8.2'square inches in the conventional completion. of a well whereas according to my concept, it will be 17.7 square inches in an offset liner in said well bore. In practice, the liner and tailpipe will be sizeddepending upon the relative gas and oil flow rates and, of course, the liquid viscosities which are expected to prevail in the well.

The liner will be slotted only over a part of its circumference. The open area will still be sufficiently great so that it will exceed the casing perforation area in most cases. Thus, whereas the casing is usually perforated withfrom four to six %-inch diameter holes giving an area of approximately .5 to .8 square inches per foot, the liner area containing slots, according to the invention, can be 24 square inchesper foot so that if only b per cent of this area is open to flow through the slots, flow will exceed the perforation flow area rates.

It is an object of my invention to provide a' gravel-packed liner for producing fluids from within well bores in the ground. It is another object of my invention to providean improved well liner of increased surface area. It is a stillfurther object of my invention to provide a combination liner and tailpipe assembly for use in well bores. It is a still further object of my invention to provide a new method for producing oil and gas from a formation. It is a still further object of my invention to provide a novel arrangement of a well-bore gravel-packed liner and tailpipe.

Other aspects, concepts. objects and the several advantages of the invention are apparent from a study of this disclosure, the drawings and the appended claims.

According to the present invention the usable area or space within which to separate gas from fluid or oil within a gravelpacked liner within a well casing is increased by positioning the normally concentric liner eccentrically in the well which permits increasing its size without any deleterious or other disadvantageous result.

It is known that gravel packs are placed within casings between liners and casing wall to minimize sand intrusion into the well. By placing gravel-packed liners within the well, a substantial reduction in casing cross section available at the bottom of the well has resulted, making it necessary to place well pumps above the producing zone and occasionally to use tailpipes, as when steaming or pumping the well. As will become evident to one skilled in the art having possession of this disclosure and having studied the same, this invention is a step toward correction of this reduction problem, since it can approximately double available liner cross section area in the casing adjacent the producing formation. Thus by positioning the gravel pack eccentrically so that the inside liner is eccentrically positioned and perforating or slotting only the area through which the formation fluids will pass through the gravel, it is possible to considerably increase the cross-sectional area, as stated.

Thisis because a larger diameter liner pipe can be used when the liner pipe is placed eccentrically.

Referring to the drawings, FIG. 1 is a horizontal cross section of a casing, taken at a production level containing a concentrically disposed gravel-packed liner according to the prior art. FIG. 2 shows an eccentrically placed, somewhat larger, liner according to the invention, perforated according to the invention. FIG. 3 is a horizontal cut across the well bore taken at a production level of a conventionally arranged casing, liner and tailpipe. .FIG. 4 shows a similar view of the offset or eccentrically disposed liner of the invention with the tailpipe adjacent to and, in part, encompassing the liner, also according to the invention. FIG. 5 is a vertical cross section, along the diameter 5-5 of FIG. 4, showing the structure of an embodiment of the invention utilized in conjunction with a down-hole pump.

Referring now to FIG. 1, there is shown a perforated casing 2, having perforations 3 and containing concentrically disposed perforated liner 4, surrounded by gravel packing 5.

Now referring to FIG. 2, there is located within perforated casing 2 a somewhat enlarged liner 6 which is eccentrically i disposed within casing 2, in this embodiment, shown to be held against the interior wall of casing 2 by positioners 7. Several positioners can be used at different levels, as one skilled inthe art in possession of this disclosure can readily determine. Gravel packing 8 surrounds, as far as possible, liner 6. The perforations in liner 6 are so disposed as to provide between them and perforations in casing 2 a decided minimum length of path of travel of the oil and gas from the formation to the perforations in the liner. This permits arresting whatever flow of sand or clay within the gravel packing, relying upon such considerations as packing size, sand-grain size, angle of repose, etc. as one skilled in these matters in this art will understand. As shown, there are no perforations to that side of the liner which is nearest the casing or touches the same. Nor are there perforations in the casing near said side of the liner. One skilled in the art will recognize that a presently perforated casing, which may be perforated around its entire periphery, can, nevertheless, have placed therein a liner arranged according to the invention. In such event, the perforations in the liner will be adjusted to provide the preferred minimum path of travel.

Considering some of the factors involved, it will be recognized that it is possible to enlarge the liner, yet enlarge the path of travel, while producing on a time basis virtually the same, if not more, actual oil of sand-free character by providing a larger diameter liner and/or a longer path of travel, there is a better separation of oil from sand as well as gas from oil as will be evident upon consideration of FIGS. 3-5. later described. The better separation of gas from oil permits pumping more oil per stroke of action of the pump, thus lifting more oil to the surface. Consideration of the factors involved, which are known to one skilled in the art. will show that the limiting factors are sand pollution and gas from oil separation to permit better pumping rather than relative size of perforations, for example. which can be adjusted, as decided, but which usually are not limiting.

Better pumping of the oil results in a lower down-hole pressure which encourages good production.

The invention is not limited to the use of a larger liner, although this is now preferred. At least the advantage of obtaining obtaining a longer path of travel in a given well by displacing the liner can be obtained by simply displacing the liner to an eccentric position. One skilled in the art will recognize upon a reading of this disclosure that various arrangements of more than one liner suitably perforated can be designed.

Referring now to FIG. 3, there is provided within a casing 2 a perforate or slotted liner 4. Within liner 4 there is provided a tailpipe 9. The annulus between casing 2 and liner 4 is packed with gravel 5 in conventional manner.

Referring now to FIG. 4, a liner is disposed eccentrically within the casing 2. There is provided, fixed to the liner l0, tailpipe 11. In this embodiment, tailpipe 11 is welded to the outer wall of liner 10. Liner 10 is perforated or slotted at 12 for the major part of its surface, except, of course, where its surface forms a wall of tailpipe 11, as at 13, and where its wall is in substantial abutment, as at 14. The space between the combination liner and tailpipe is filled with gravel in a conventional manner.

It is recognized that the liner of FIG. 3 is slotted around its circumference. However, with the arrangement according to the invention, oil production is considerably speeded up for the same size external casing and liner. There is better gas from oil separation.

Referring now to FIG. 5, oil enters casing 2 through perforations 3 and into liner 10 through perforations 12. Gas separates from the oil and passes upwardly while the oil which settles into the bottom of the liner passes through port 15 into tailpipe 11 and upwardly therethrough and is pumped by pump 16 up through the piping string thereabove (not shown)to the surface of the ground.

One skilled in the art in possession of this disclosure having studied the same will understand that the drawings are diagrammatic in character and that they have been sketched for purposes of illustration only. Details of some items, such as packer 17, the joint of tubing stinger l8 and the top of the liner-tailpipe combination at the O-rings 19 have been either simplified or omitted.

As shown in FIG. 4, the combination of the liner and tailpipe is so sized as to just fit into the casing 2. At points along the length of the combination assembly at which the overall size of the liner and tailpipe is insufficient to position the same in the casing, there can be, and usually will be, used positioners at about each b 10 to 20 feet of depth.

Although not now preferred, some or all of the oil can be pumped up through a tailpipe positioned within the liner will be evident to one skilled in the art having studied this disclosure and its concepts.

EXAMPLE In a 7-inch, 20 -pound casing with a 3 %-inch FJ. slotted liner, the central area is 7 square inches. According to the invention, this area is increased to 12.1 square inches, using a 4 inch liner. The slotting is arranged to carry the oil. There are always enough slots so that the total opening is ample to carry the oil. This in is not a limiting factor.

Reasonable variation and modification are possible within the scope of the foregoing disclosure, the drawings and the appended claims to the invention the essence of which is that a liner and/or a tailpipe combination has been provided wherein the liner is eccentrically disposed in a well bore or casing so that the well bore area adjacent producing sand, which is available to run a tailpipe through gravel-packed space between the liner and the casing, can be run or positioned within the well.

I claim:

1. In a well a well bore casing pipe, a perforate liner pipe extending substantially toward the surface for delivery of fluid therethrough, said liner pipe being eccentrically disposed within said well bore casing pipe, said liner pipe being packed in gravel in said well bore casing pipe, there is provided within the area between the liner and the well bore casing pipe a tailpipe extending down to a point below the main body of the liner so as to pump fluids in or out of the well at the bottom or below said liner, and wherein the tailpipe is structured by welding an arcuate segment of pipe to the wall of said liner which is removed from the wall of the well bore casing pipe so that a portion of the wall of said liner also forms a portion of a wall of said tailpipe and said liner is perforated only in a part of its wall which is not serving as a wall of said tailpipe and not closest to the wall of the well-bore casing pipe.

2. A structure according to claim 1 wherein the liner is perforated only at points sufficiently away from that part of the well bore casing pipe to which it is nearest to permit a minimum path of travel through the gravel packing to the perforations in said liner.

3. A structure according to claim 2 wherein the well bore casing pipe and the liner are each of them perforated sufficiently far away from the point at which they most nearly approach each other so as to provide a minimum path of travel from the perforations in the casing through the gravel packing to the perforations in the liner.

4. A method for producing a fluid from a producing formation in the ground employing a gravel packed perforated liner which comprises positioning into a well bore substantially adjacent a producing formation a perforated liner off center with respect to the axis of the well bore, said liner being perforated or slotted or otherwise adapted to receive into its cell, fluid from without said liner which collects in the well bore, said liner being perforated only over a part of its circumference, packing said liner in an eccentric position into said well bore with gravel or similar material with its nonperforate portion adjacent the wall of the well bore and so that there will be gravel adjacent said perforated portion, and producing fluid from said formation and well bore through said gravel and into said liner through the perforate portion thereof and from within said liner.

5. A method according to claim 4 wherein a tailpipe extending toward the bottom of said liner is placed in juxtaposition thereto and the fluid is pumped from within the bottom of said liner up through said tailpipe.

6. In a well a well bore casing pipe, a perforate liner pipe eccentrically disposed within said well bore casing pipe extending substantially toward the surface for delivery of fluid therethrough, said liner pipe along its length being packed in grave] within said well bore casing pipe to permit oil and gas to flow thereinto from the gravel-occupied space surrounding the liner and a tailpipe within the area between said liner pipe and said well bore casing pipe extending down to a point below the main body of the liner pipe wherewith to pump out fluids collecting and from within said liner pipe.

7. An apparatus for producing a fluid from a formation in the ground comprising a well bore casing pipe, a perforate liner pipe extending substantially toward the surface for delivery of fluid therethrough, said liner pipe being eccentrically disposed within said well bore casing pipe, said liner pie pipe being packed in gravel in said well bore casing pipe, a tailpipe extending down to a point below the main body of said perforate liner pipe within said well bore casing pipe within the area between said liner pipe and said well bore casing pipe wherewith to pump fluids in or out of the well through said perforate liner pipe, said liner pipe being perforated only in a part of its wall and not in that part of its wall closest to the wall of the well bore casing pipe. 

1. In a well a well bore casing pipe, a perforate liner pipe extending substantially toward the surface for delivery of fluid therethrough, said liner pipe being eccentrically disposed within said well bore casing pipe, said liner pipe being packed in gravel in said well bore casing pipe, there is provided within the area between the liner and the well bore casing pipe a tailpipe extending down to a point below the main body of the liner so as to pump fluids in or out of the well at the bottom or below said liner, and wherein the tailpipe is structured by welding an arcuate segment of pipe to the wall of said liner which is removed from the wall of the well bore casing pipe so that a portion of the wall of said liner also forms a portion of a wall of said tailpipe and said liner is perforated only in a part of its wall which is not serving as a wall of said tailpipe and not closest to the wall of the well-bore casing pipe.
 2. A structure according to claim 1 wherein the liner is perforated only at points sufficiently away from that part of the well bore casing pipe to which it is nearest to permit a minimum path of travel through the gravel packing to the perforations in said liner.
 3. A structure according to claim 2 wherein the well bore casing pipe and the liner are each of them perforated sufficiently far away from the point at which they most nearly approach each other so as to provide a minimum path of travel from the perforations in the casing through the gravel packing to the perforations in the liner.
 4. A method for producing a fluid from a producing formation in the grounD employing a gravel packed perforated liner which comprises positioning into a well bore substantially adjacent a producing formation a perforated liner off center with respect to the axis of the well bore, said liner being perforated or slotted or otherwise adapted to receive into its cell, fluid from without said liner which collects in the well bore, said liner being perforated only over a part of its circumference, packing said liner in an eccentric position into said well bore with gravel or similar material with its nonperforate portion adjacent the wall of the well bore and so that there will be gravel adjacent said perforated portion, and producing fluid from said formation and well bore through said gravel and into said liner through the perforate portion thereof and from within said liner.
 5. A method according to claim 4 wherein a tailpipe extending toward the bottom of said liner is placed in juxtaposition thereto and the fluid is pumped from within the bottom of said liner up through said tailpipe.
 6. In a well a well bore casing pipe, a perforate liner pipe eccentrically disposed within said well bore casing pipe extending substantially toward the surface for delivery of fluid therethrough, said liner pipe along its length being packed in gravel within said well bore casing pipe to permit oil and gas to flow thereinto from the gravel-occupied space surrounding the liner and a tailpipe within the area between said liner pipe and said well bore casing pipe extending down to a point below the main body of the liner pipe wherewith to pump out fluids collecting and from within said liner pipe.
 7. An apparatus for producing a fluid from a formation in the ground comprising a well bore casing pipe, a perforate liner pipe extending substantially toward the surface for delivery of fluid therethrough, said liner pipe being eccentrically disposed within said well bore casing pipe, said liner pie pipe being packed in gravel in said well bore casing pipe, a tailpipe extending down to a point below the main body of said perforate liner pipe within said well bore casing pipe within the area between said liner pipe and said well bore casing pipe wherewith to pump fluids in or out of the well through said perforate liner pipe, said liner pipe being perforated only in a part of its wall and not in that part of its wall closest to the wall of the well bore casing pipe. 